Estrus suppression boosts gilt welfare, productivity in Canada
Delaying sexual maturity in gilts is helping pig producers in Canada streamline their production systems while improving carcass quality and animal welfare.
The process involves the use of an immunological product that stimulates the pig’s immune system to inhibit gonadotropin-releasing factor (GnRF), a naturally occurring hormone that triggers the onset of puberty.
Working in the same way as a vaccine, the product is administered twice: once when the pigs are typically 10 to 11 weeks old to prime their immune system, and again toward the end of the finishing period at about 5 to 7 weeks before marketing, at which point the immunization’s puberty-delaying effect kicks in.
Initially, the technology was developed for use in male pigs to reduce boar taint without having to physically castrate. Now, it is also being used in several markets to temporarily suppress estrus in gilts, with producers observing performance, management, welfare and quality benefits in both males and females.
For producers in countries like Canada, where mixed-sex housing systems are common, the ability to give the immunization to both gilts and boars at the same time offers significant advantages, says Leanne Van De Weyer, DVM, Zoetis swine veterinary services manager.
“In the past, farmers using mixed-sex housing who wanted to immunize boars needed to separate them from gilts prior to administration,” she says, noting that the product has been registered for use in male pigs in Canada since 2011.
“This meant that it wasn’t feasible for some producers, as sorting the animals was too labor intensive.
“We had mixed-sex farms using the technology to a small degree on their males, but they were very clear that they couldn’t consider large-scale use unless it could be administered to gilts too.”
Following trials to establish the product’s safety and efficacy in gilts in Canadian systems — including mixed-sex ones — approval was granted by Canada’s Veterinary Drugs Directorate in 2016.
Since then, producers have been introducing the procedure into mixed-gender systems, helping make significant improvements in welfare, production throughput and carcass quality, Van De Weyer says.
According to Van de Weyer, one important benefit in gilts is increased feed intake following the second dose of the product, as their sexual behavior declines.
“Feed intake in treated gilts increases after the second dose; as a result they usually gain weight more quickly than gilts that are allowed to progress to sexual maturity. In a trial in a commercial system in Canada, we observed treated gilts reaching market weight an average of 6 days faster than control animals, and just because they do not cycle,” she says.
“That’s incredibly important for efficient barn-space utilization, and it means immunized gilts are matching immunized males more closely in reaching target weights, so mixed-sex batches are more uniform,” she adds.
“Obviously, that varies according to genetics and feeding schedules, but if you can match growth and turn over barns more efficiently, that’s money in the bank.”
Because of the increased feed intake in both immunized gilts and males, it’s important to formulate cost-efficient diets, Van De Weyer says.
“Many producers who immunize gilts started out with males, so they have come to a good understanding of what’s needed from a nutritional standpoint. Many have done their own feed trials and have worked with nutritionists to develop cost-appropriate rations.
“Aside from the faster growth, we also see carcass benefits for immunized gilts,” she adds. “In all of our trials we observed an increase in carcass weight, belly weight and back fat.
“That can be advantageous for customers who are selling fresh pork to Asian markets that demand high-quality, specific cuts of pork.”
Another important element of administering the product to both gilts and boars is the impact it can have on animal welfare, Van de Weyer says.
“Because of the trend in North America toward increasing market weights of swine, an increasing proportion of gilts reaches puberty before reaching the end of finishing,” she explains.
“Females in estrus can exhibit decreased time spent eating, as well as behavioral changes such as mounting. This can affect growth performance and potentially lead to injuries, particularly in mixed-gender housing.
“While farmers in Canada don’t produce entire males, in countries that do it’s worth bearing in mind that increased cycling in mixed herds also means there’s a risk some females will be going to slaughter pregnant,” she adds.
“It’s a welfare issue that as an industry we should be considering, and this puberty-delaying technology is one way of addressing it.”
Addressing consumer concerns
As consumer concern about animal welfare increases, Van De Weyer hopes there will be more opportunities for Canada’s producers to increase their use of alternative technologies in the future.
“In Canada, there is growing industry recognition that consumers are concerned about animal welfare and would not support physical castration of pigs, especially if they knew an alternative was available,” she adds, noting that consumer surveys in the US, Canada and Europe have consistently demonstrated high consumer acceptance of the immunization approach.
“Some of the challenges we face with uptake — whether it’s used in gilts or males — reflect uncertainty about the attitude of meat buyers. Although studies have rigorously established the safety and efficacy of this immunization, Canada exports over 70% of the pork it produces, so packing plants are cautious about any possible concerns.
“However, this product is licensed for use in more than 65 countries — including all of the major pork-producing countries. As it becomes more globally recognized, opportunities for its use will continue growing.”
Posted on April 23, 2019